ADB: Phone is not recognised but Ubuntu 18.04 recognises it

My LG G3 phone (phone is rooted; OS is Android Fulmics ) is recognised by my laptop when I plug it in. The laptop is running Ubuntu 18.04 and I can easily copy data from and to my phone. I have recently installed the Android Debug Bridge (ADB) (sudo apt-get install android-tools-adb). Then, I wanted to reach my device and typed adb devices. When functioning properly, it **should** return something like this : * daemon not running. starting it now on port 5037 * * daemon started successfully * List of devices attached 5200d6fd904b2200 device But when I tried it, it returned this: List of devices attached * daemon not running. starting it now on port 5037 * * daemon started successfully *   So, List of devices attached appeared **first** and no device was listed. When I type adb devices again, I get this: List of devices attached   I have also tried to use sudo adb devices instead of adb devices but the results were the same. When the ADB would work, I would try to use it for data recovery purposes as described here . Maybe the pull command can do what I want.